Color phasing system



COLOR PHASNG SYSTEM Filed Sept. 10, 1949 2 SHEETS-SHEET Jl.

'f' *7i/Z gil@ fi ""Hl lh, Z4

q z a if a za g ATTORNEY Feb. 3, 1953 A. N. GoLDsMl'rH 2,527,548

vCOLOR PHASING SYSTEM Filed sept. 1o, 1949 2 SHEETS-SHEET 2 ATTORNEY Patented Feb. 3, '1953 COLOR PHASING SYSTEM Alfred N. Goldsmith, New York, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application September 10, A1949, Serial No. 115,049

4 Claims. l

This invention relates to means for maintaining a desired relation between the transmitted and received intelligence conveyed by a colortelevision system. It has for its principal object the provision of an improved apparatus and methodof operation whereby a desired relation is maintained between the color-separation sig nals of the transmitter and the color component images produced by the receiver.

As is well known, there are sent from a colortelevision transmitting station a recurrent sequence of video signals. These signals each represent a diierent color-separation component of an element or a field or frame of the subject matter. Thus for each component there are transmitted different signals of a group number dependent on the number of selected colors and this number of signals is for each of the components. For purposes of illustration, it will be assumed that the selected colors are red, green and blue.

In the event that the color-television receiver utilizes the conventional color-disc or drum filter (or any equivalent electromechanical or electronic device) it is of course essential that the scanning of the red separation image at the re ceiver shall be effected by the red separation signal from the transmitter. This is also true of the green and blue images. It is therefor necessary that there be provided automatic means whereby some form of discriminating signal is sent from the transmitter which indicates the color of the scanned eld and Ithat there shall be at the receiver means whereby the corresponding color lter is placed between the originally reproduced image and the eye of the observer.

In accordance with the present invention, this result is accomplished by optical means, electromechanical means or electronic means. In the case of each of these different means, there is produced at the transmitter a signal which occurs at a pre-determined point in the scanning cycle and this signal is utilized at the receiver to insure that the color-selective element of the receiver corresponds to the proper color-separation signal.

Essentially the method herein disclosed utilizes at least one spot of a primary or component color corresponding to that oi the image under transmission for use as an identifying signal. The spot of the color in question is so placed as to be invisible to the viewer of the vreceived image. This is accomplished by placing the identifying component-color spot in that portion of the scanned rectangular image area which is masked off by the rounded corners of the picture as viewed at the receiver.

In one form of the invention, the identifying component-color spot is produced by means of a small light beam which is projected to the photoelectric mosaic of the camera through the same color disc as the image of the subject; matter to be transmitted. Alternatively this small light beam may be projected to the mosaic of the camera through a separate color disc.

In another form of the invention, the outputs of the eld deflection and line dcection genera tors are combined in a manner to produce a 'voltage which is `applied to the control grid 4of the camera and may be controlled to intensify its cathode ray at any desired point in the scanning cycle.

In a further form of the invention, commutators rotating respectively at frame and line frequencies are utilized to provide a signal at the desired point in the scanning cycle. Like the signal produced by the identifying light spot, previously mentioned, this signal is transmitted with the vdeo signals and is utilized at the receiver to effect proper color phasing between the video signals and the observed images at the receiver.

The invention will be better understood from the following description considered in connection with the accompanying drawings and its scope is indicated by the appended claims..

Referring to the drawings:

Figure 1 indicates the usual rectangular .scanning field at a transmitter or receiver and shows the observed lield as dened by a mask having rounded corners at its inner periphery.

Figure 2 illustrates different forms of identifying spots which are produced in the masked corners of the scanning eld.

Figure 3 illustrates a form of the invention wherein the identifying color-component spot is produced by a small beam of light transmitted to the camera mosaic through the same color disc as the image of the subject matter to be transmitted.

Figure e illustrates a form or color disc which may be utilized separately from the color dise through which the image of the'subject matter is projected to the mosaic of the camera.

Figure 5 illustrates a pair of commutatore which are rotated at frame and line speeds re spectiveiy for producing a signal at a selected point in the scanning cycle.

Figures 6 and 7 illustrates a form of the inven# tion wherein the outputs if the iield and line deiiection generators are combined ina'inanner to vary the intensity oi the Vcamera beam at a predetermined point or points in the scanning cycle.

Figure 8 illustrates on an enlarged scale one corner of the scanned held and the mask of Figure 1.

Figure 9 illustrates how the transmitted identifying signal is utilized in the image tube of the receiver.

Figure illustrates the relation between various parts of the television transmitter.

Figure 11 illustrates the relation between the. various parts of the receiver.

As Will appear, parts of the transmitter and receiver which are conventional in the art are shown in the form of boxes bearing explanatory legends.

In Figures 1 and 8 the usual rectangular scanning eld is indicated by the dotted lines I. This field is masked sothat only that part of it within the full line I I is exposed. As indicated at I2v and I3, the colon-,component spots for producing the identifying or color-phasingsignal are produced in an area of the scanning field which is covered, bythe mask.

These spots may be of any suitable form such ssihoss shown bv (o), (D), (o), and (d). of Figure 2, for examples, and they may occur in only a single corner ot the image, or in. several corners.

Figure 3v shows one arrangement suitable for producing these color-componentsy spots. In this fig-ure, are shown a color disc I4 and a part of the mosaic I5l of the television transmitter camera. All image of the subject metier to be transmitted (not shown), is. projected. through the upper loert of the disc I4 to the mosaic I5 in a manner new espressione-.1. in the. ert- The color-.component snot produced si sy point ti of the mosaic is by means including a light source I1 which emits light through a masi; I8 having a small aperture I9, The beam thus formed is projected through the lower part of the disc I4 yand a lens 29 to the Point I5, oi the. mosaic The. light projected through the lens and the disc Ie may be made toy have the same coloras that applied through the upper part of the disc.

In this purely optical method oi creating the Ycolor spot. it is. clear that this bright spot of c0101 will drown out any other col-ors in the corner of the image and Will impress a color signal offull brightness, and oi corresponding component color of that held,y upon the modulator of the colorteleivision transmitter as that portion of the mo is. flamled.-

As indicated by Figure 4, the light beam applied to the, Point l5 oi the mossic. l5 may bo projected through a separate color disc 2l instead of through the disc I 4. In this case, the disc 2l is. reiste@ simultaneously with, tho diss lo. and in Color chess therewith Thus it may have ons color sector 22 (e. g. red), and sectors 23 and 2e h ff'e. QPEPQQC:

guise 5 illustrates an electromechanical form of device Iadapted to produce the color-phasing Sigllll P12 .h IQnt. l@ .0f the @95am 5i 0f Figure 3 This dev-iso. includes ons computato? 25 which is rotated et trofeo frequency and another commutator g5 which is rotated at line frequency. When i511? :Ylall'QW Gliznllctlf? Segments 0f these twol commutatore simultaneously engage their cooperating brushes! so elootiiosl pulso from s source (not shown) is transmitted from a lead 2l' through the commutatoi-'s and a lead 28 toproduce a color-phasing signal which is utilized as previously molestos- Tho two oomofiuieiols are conductive `only during the time when the video signal is derived from a portion of the image area nea-r one of its corners. In this case, the denf tifying or color-phasing spot is not produced at the point I6 but its electrical effect is duplicated.

Figure 6 shows the conventional field deflection wave of a television transmitter. A small section of the Wave near peaks 29 and 3l) corresponds to the scanning of one corner of the image.

Figure 7 illustrates acir'cuit adapted to vary the` intensity of the cathode ray of the camera at one corner of the scanned field. This circuit includes a field deection generator 3 I which delivers an output Wave similar tothat ci Figure 6. A similar wave` oi higher frequency is produced at the output of a line deflection generator 32. Output from the generators 3| and 32 is supplied through leads 33 and 34 respectively to the eld and line deflectionA systems of the transmitter camera. Through a lead 35 output is also supplied from the generator 3l to an amplifier 36 which has applied to its input lead 3l a voltage such that it is biased on only when the output voltage of the generator 3i is above the level indicated by the line 38 of Figure 6.

The amplier 3S delivers its output to the input ofan amplifier 33. The input of this amplifier 39 also is connected (l) through a lead e0 t0- the output of the line deflection generator 32 and (12) through a lead lll to a source of bias voltage having a value such that the amplifier 39 conducts only near the peaks of the line deflection voltage. Under these conditions, the output voltage of the amplifier 39 is increased only in the corresponding portions of both the eld deflection wave and the line deilection Wave.

The output voltage of the amplifier 39 is applied through .a brightness control circuit 52 of conventional form to the grid of the transmitter camera which is indicated in Figure '7 bv the reference numeral (i3. As a result, the beam current of the camera 43 is changed in a manner to cause a full-,output component-color signal at selected points in the scanning cycle, regardless of the image showing on the mosaic at that point.

Figure 9 indicates how the component-colorphasing signal, produced as indicated above, may be utilized at the receiver to insure propel' phasing between such signals and the reproduced images of the transmitted subject matter. This igure shows one corner of the image tube which may be ot any of the suitable forms conventional in the art, The image tube is illustrated as having at one of its ends a fiucrescent screen M to which a scanning beam Y45 is applied. The spot produced on the screen 43 by the color-phasing igual is indicated at 16s-fil. In front oi the screen 511:41 is mounted a mask. 53 having the inside periphery, I I of Figure 1 and having a cavity 49 Within which is mounted'a light responsive tube 50. Interposed between the tube 58 and the spot Effe? is an aperture 5 I. A filter 52 having a color corresponding to the color-phasing signal transmitted throughv the beam '55 to the spot @15e-.4.1 may be mounted so es to Cover tho atei'- tiuo 5l- It will be noted that the tube 5d is nested Within the masking framework over the kinescope or image reproducing tube and is invisible to the observer'. The output of the tube 5i) is utilized to control the color phasing deviceby Whatever means are suitable for the particular'type oi re- @giver which is used- Figure l0 illustrates in a general way one p ossible relation between the various parts of a colortelevision transmitter. This transmitter includes a camera 53 which includes (i) an electron gun 54 for producing an electron beam indicated by a broken line 55, (2) the mosaic or target electrode I5, (3) deflector coils 58 for causing the beam to scan the mosaic l5 in a well known manner, and (4) an electrode 51 for collecting the electrons released from the mosaic.

An image of the subject matter to be transmitted (not shown) is projected through a lens 58 and the color disc I4 to the mosaic I5. The speed of the disc I9 and the scanning frequency are so related that the mosaic I5 is scanned once for each color lter interposed between the subject matter and the mosaic. As a result, there Iare produced at the output lead 59 of the camera signals each of which is representative of a clifferent component-color of the subject matter.

At the point I9 in each scanning cycle, there is also produced a color-phasing signal which is also made available at the output lead 59.

These video and color-phasing signals are am plified by an amplier 69 and supplied through a lead 5I to a transmitter (not shown).

The radiated signals are received by an antenna (not shown) from which they pass through conventional circuits to a receiver 68 wherein the video and color phasing signals are separated from the synchronizing signals. From the receiver 63, video signals pass through a lead 59 to the control grid of the image tube or reproducer 19. The synchronizing signals are supplied through a lead 1I, to an oscillator 12 which has its output connected to the bi-directional scanning coils 1314 by which the electron beam of the image reproducer 1i! is made to scan the iluorescent screen 49.

As pointed out in connection with Figure 9, the screen all is masked by a member 98 having at one of its corners a cavity within which is nested the photoelectric cell 59. The images appearing on the exposed area of the screen 44 are projected through a color disc 15 to the eye of the observer.

Between the fluorescent screen 44 and the photocell 59 is interposed a color filter 1B which is selective to the color corresponding to the transmitted phasing signal.

Rotation `or the disc 15 is effected by a motor I1 in a manner similar to that disclosed by a patent of G. L. Beers, 2,378,746. The motor 11 is mechanically coupled to the disc 15 through a reduction gear 18 and a clutch 19-89. clutch is controlled by a solenoid BI which is energized by a source B2 and an associated ampliiier 9| when the spot I6 is illuminated and the position of the disc 15 is such as to pass the light selected by the filter 18. For example, if the filter 16 transmits red light, the solenoid 8l is energized when (1) the red sector of the disc 15 is aligned with the lter and (2) the spot I6 is illuminated. If the red sector of the disc 15 is not aligned with the filter when the spot I6 is illuminated, the current of the photocell 59 is reduced and the solenoid 8l is deenergized.

Associated with the clutch members 19 and 88 are a collar 83 which is movable along the shaft 84 and la dog 85 which is pivoted at 86 and is biased to its illustrated position by a spring 91.

In this position, the dog 95 engages one or` another depression in the plate 80 so as to lock the shafts 84 and 88 in any one of the different positions corresponding to the differently colored sectors of the disc 15.

The position of the collar 83 along the shaft 84 is determined by a member 89 which is biased to the right by a spring 90 but is maintained in This its illustrated position so long as the red sector of the disc 15 comes into alignment with the iilter 16 while the spot I6 is illuminated. When this condition does not exist, however, the solenoid 8I is deenergized, the collar 83 and member 99 are moved to the right by the spring 99 and the dog is operated to disengage the plates 19 and 89 so that the plate 89 slips until proper color phasing is eiected.

What the invention provides is an improved color phasing system which functions during the scanning of an unobserved area of the scanned field to produce a signal which is utilized at the receiver for maintaining a desired relation between component colors of the transmitted subject matter and its reproduced image.

I claim as my invention:

1. In a color television system utilizing color separation images and in which portions of the reproduced image at the receiver are normally masked from view, means for producing a desired phase relation between the transmitted and reproduced color separation images comprising in combination means at the transmitter for producing color phasing pulses, means adding said pulses to the transmitted signal train at periods corresponding to time intervals during which the scanning beam is scanning one of said portions masked from view, means at the receiver utilizing said color phasing signals to activate the receiver mosaic at at a corresponding one 'of said masked portions, means also at the receiver for adjusting said phase relation, and color sensitive means responsive to the activation of said masked portion for operating said phase adjusting means `to establish said desired relation.

2. A color television system in accordance with claim l in which said color phasing pulse producing means comprises an optical system arranged to saturate a portion of the image mosaic corresponding to one of said masked portions with light of a single color component.

3. A color television system in accordance with claim 1 in which said color phasing pulse producing means comprises a source of vertical deflection voltages, a source of horizontal deflection voltages, means combining said voltages so as to produce a control voltage when the peaks of said deflection voltages coincide, and means utilizing said control voltage to produce said color phasing signals.

4. A color television system in accordance with claim 1 in which said color phasing pulse producing means comprises a commutator operating in synchronism with the horizontal scanning, a second commutator operating in synchronism with the horizontal scanning, said commutators being connected in series, a source of potential connected to said commutators, and means for deriving from said source and said commutators said color phasing signals.

ALFRED N. GOLDSMITI-I.

REFERENCES CITED The following references are of record in the nle of this patent:

UNITED STATES PATENTS Number Name Date 2,309,506 Herbst Jan. 26, 1943 2,319,789 Chambers May 25, 1943 2,378,746 Beers June 19, 1945 2,339,979 Huffnagle Nov. 2'1, 1945 2,530,431 Huffman Nov. 21, 1950 

